Unless I'm mistakingly, isn't feminism centered around "freedom of choice?" So the real question should be, why do women need to a plastic surgery? To feel good about themselves or to make themselves look appealing to someone else?

When you are worried about how people see you, then, it's wrong to do anything that pleases people. If your firend must enhance her body, then she should do it for herself, not for someone else. Because no one will care when she experiences any side effect from her procedure.